Flash memories widely used as nonvolatile memory devices are regarded as being limited in the improvement of integration density. As a nonvolatile memory device enabling a higher integration density than flash memories, a cross-point nonvolatile memory device has been drawing attention. The cross-point nonvolatile memory device is configured so that, for instance, a memory portion having variable electrical resistance is sandwiched between two electrodes (JP-A 2007-184419 (Kokai)). Furthermore, there is also a nonvolatile memory device having a three-dimensional structure in which the aforementioned cross-point nonvolatile memory devices are stacked.
In this case, the first-layer memory portion and the second-layer and higher memory portion stacked thereon are subjected to different histories (e.g., thermal histories) associated with e.g. treatment during the manufacturing process. Hence, these memory portions become different in electrical characteristics. This causes the problem of being difficult to realize stable operation in memory retention and reading.